Before starting this work, I knew nothing about Blender or even 3d but I had good notions of image processing . Yet it is on this last point that I need your expert advice I work with Gimp and Paint.net .
When I load my files to sims4 Studio DXT5 as it should (type iterative compression) , most of my painstaking work deteriorated and as you can see I have many blurry parts .
That said, every advice would be welcome , even if they do not apply to this specific problem. In the rar file you will find two files package, and two blend files that match .
( Be friendly to use simple words, I am French and I master very bad English language ... )

Moving to Create > CAS Parts.

DDS compression is not lossless -- I haven't looked at your file (can you post screenshots instead of making people download the whole thing?), but what sometimes helps is to add noise to the texture. Most image editors should have a noise filter somewhere.

I'll post more pictures later if necessary, for now I just expose this one to show what I mean

Ah OK; adding noise will probably not help you with that. Looks like normal compression artifacts to me. Maybe you can try a different kind of compression filter; see the sticky in Tools for pointers (Tools like Aorta or dxtbmp might have more options than Gimp; I don't use that so I don't know how it compares).

Ihave no choice, the game just accept bc3 / dxt5 compression. Today I tried lots of options : no mipmaps, mipmaps with filters, wrap mode, gamma correction, ... the result is alway the same. Yet when I look at the mods on this site , I see that it is possible to obtain a good resolution . Could someone please tell me how ?

You can't turn off mipmaps, that won't work. I meant that you could try different kinds of filters, depending on which tool/s you use the options will vary .. here is a bit of an overview, perhaps that helps you to compare: http://sourceforge.net/p/nvidia-tex.../ResizeFilters/



Which "mods on this site" do you mean, can you give an example?

I am not an English language expert
I just wanted to say the other uploads, the mods shared on this site, are all clean, no blurr and I don't know what to do for having the same quality. I have a lot of mods I download in Mts, that's the reason I would like to share at my turn ...

I went on the link but it does not do me much. It made me still possible to explore other possibilities.
Anyway, thank you for your help